פירוש על בראשית 21:14

לחם וחמת מים BREAD AND A BOTTLE OF WATER — but not silver and gold, because he hated him for taking to degenerate ways (Exodus Rabbah 1:1).

AND THE CHILD, AND HE SENT HER AWAY. This is to be understood in connection with the above: And he gave to Hagar [the bread and bottle of water]… and the child, for he gave her the child also to go with her wherever she will go.

ותתע במדבר באר שבע, that is why she ran out of water, a supply of which she had carried with her. Avraham had given her a big enough supply if she would have taken the direct route to Beer Sheva.